Mitosis - Biology 111 Principles of Biology Lecture...

Biology 111, Principles of BiologyLecture OutlinesCell Division & Mitosis:There are two basic mechanisms by which organisms reproduce:ASEXUAL reproduction involves only a single parent (e.g. cell division) Progeny are genetically identical to the parentSEXUAL reproduction involves the fusion of two sex cells (e.g. sperm & egg)Each parent makes an equal genetic contribution to the offspringExcept in true-breeding lines, offspring tend to show variability among individualsExcept in true-breeding lines, offspring tend to be different from parentsAt the cellular level, both sexual and asexual reproduction require a division of cellular contents (organelles and chromosomes) between progeny cells.Chromosome organization in prokaryotes & eukaryotes:ProkaryotesEukaryotesDNA free in cytoplasmDNA enclosed in nucleusSINGLE circular DNA moleculeMULTIPLE linear DNA moleculesPLASMIDS (mini-chromosomes), usually many copies (30 - 200)Generally NO plasmidsDNA segregated by attachment to the cell membraneDNA segregated by attachment to spindle--a microtubule structure designed to move chromosomesOne primary "signal" for cell division is related to SIZE:In the life-cycle of cells, they first grow and then they divide.

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